1. Field of the Invention
The present disclosure relates to a two-dimensional fiber array structure, more particularly to the fiber array structure including a base which includes a baseboard, a cover board and a spacer layer, and an optical fiber cable is positioned between the baseboard and the cover board, positioning fibers are positioned at two external sides of the optical fiber cable, the spacer layer is abutted with two adjacent fiber layers of the optical fiber cable to reduce the position tolerance along X axis for further improving accuracy, whereby ensuring quality and stability of transmitting optical signal.
2. Description of the Related Art
In recent year, as communication technology and Internet Network are rapidly developed, data center and telecommunication venders continuously make effort in products with high density, high transmission rate, large volume and intelligent functions. In order to satisfy requirements in higher data transmission rate, smaller occupied space and lower power consumption, many companies pay more attention in a fiber transmission system which is an important constituent of physical infrastructure. Because of having advantages of larger bandwidth, higher transmission rate, longer transmission distance, thinner volume, better anti-EMI and good confidentiality, the fiber transmission system has been widely applied in many fields.
In basic architecture of the fiber-optic communication, a transmitter converts electric signal into optical signal, the optical signal is then transmitted to a receiver through an optical fiber cable, and the receiver converts the optical signal into the electric signal for receiving. A fiber array having a high optical coupling rate is a best-choice product under a condition that the transmission bandwidth is increased and channel requirements becomes more. The fiber array is an important device connected between the optical fiber cable and a pairing device, and mainly applied in connection between the optical fiber cable and PLC, DWDM system, OXC, OADM, optical router or optical switch. In a manner of installing the fiber array, the fiber array and a laser diode array are aligned first for splice therebetween. For alignment, it is necessary to find the location where the maximum optical coupling rate exists between the laser diode array and the fiber array, so as to facilitate splicing process later. In other manner, the alignment of optical coupling location is omitted before the fiber array and the laser diode array are spliced, and the package yield is mainly dependent on the manner of splicing and positioning the fiber array and the baseboard, such as manner of adhesive, soft-soldering or laser welding.
In the conventional fiber array, a glass baseboard includes a cover board and a chip which includes a plurality of longitudinal V-shaped grooves. A plurality of fibers are respectively disposed in the V-shaped grooves of multiple glass substrates, and the multiple glass substrates are then stacked to form the conventional fiber array. The fibers are respectively positioned by the V-shaped grooves to ensure the alignment accuracy of the fibers. The number and density of fibers can be adjusted upon requirement, so as to implement more compact fiber array and miniaturization package. Please refer to FIG. 11. A plurality of fibers B are respectively disposed in the V-shaped A1 of the stacked glass substrates A, and epoxy resin are used for package to form adhesive layers C. However, the surface of the glass substrate A must be carved by a cutting tool to form the V-shaped grooves A1 one by one, which causes long process time and is easy to break the glass substrate A. Moreover, a tolerance may be generated after every machining process by the cutting tool, so the position accuracy of each of the fibers B of the fiber array is reduced, and the quality of transmitting the optical signal through the fiber B is degraded. In addition, the pitch between the two adjacent layers of the fibers B is limited by the capacity of producing the glass baseboard A and the maximum depth of the V-shaped groove A1. In fact, it is very difficult to produce the glass baseboard A with a thickness smaller than 0.3 mm, and multiple processes and stack of layers of the glass baseboards A also cause high cost in keeping accuracy of the fiber array and lower yield rate. In addition, the parallelism between two ends of the glass baseboard A is also not easy to achieve. Therefore, it is very hard to reproduce the high-end fiber array having the fibers B with high-density and micron-level position accuracy.
Some manufacturers use photolithography etching process technology to form the V-shaped groove, so as achieve accuracy and miniaturization of the baseboard. However, this technology is only adapted to the fiber array which uses a wafer as the baseboard, and also has disadvantages of complicated wafer process, material limitation and high cost, which results in bottleneck for application, for example, quick mass production and cost reduction cannot be achieved easily, and the process may cause environment pollution and be not environmentally-friendly. With continuous progress of the material technology, new glass material and plastic material are developed to produce the baseboard by a manner of compression molding or injection molding, so as to reduce the production time of the baseboard. However, after assembly of the baseboard and the plurality of fibers, the epoxy resin is heat-shrinkable or stress-deformable easily to shift fibers, which may result in poor package yield of the fiber array and more insertion loss.
Please refer to FIG. 12. The glass substrate A is coated with epoxy resin on a surface thereof, and the plurality of fibers B are then respectively disposed into the V-shaped grooves A1 of the glass substrate A to form staggered-stacked arrangement, and the cover board D is then placed on the glass substrate A to downwardly abut the V-shaped grooves D1 thereof with outer surfaces of the plurality of fibers B, so as to pinch and position the plurality of fibers B. Next, the epoxy resin is cured to form the adhesive layer C integrally. The stacked structure of the plurality of fiber B can greatly save product space and provide higher position accuracy (such as, about 1 μm to 2 μm). However, the plurality of fibers B are hardly to shift along X or Y axis subject to constraint of the stacked structure, and machining process for the V-shaped grooves A1 and D1 of the glass substrate A and the cover board D may cause tolerance, so the problem of position tolerance and accumulated error are also generated to make the fibers B easily shifted when the stacking number or disposal number of the fibers B is increased, which results in reduction in position accuracy of each of the fibers B of the fiber array. Moreover, when each of the fibers B has different accuracy, the insertion loss may be increased and the return loss is decreased, thereby impacting quality of transmitting optical signal.
In conclusion, what is need is to design machining process and structure of the fiber array to contain more number of the fibers and provide better precision of package with lower cost, so as to meet the requirement in the practical application of the fiber array.